The Deep End (2001)

In the comfort of a seemingly ordinary life, Tilda Swinton brings to the fore a sense of isolation as Margaret Hill, a lonely Lake Tahoe housewife whose naval officer husband spends months at sea on an aircraft carrier. In his absence, Margaret does her best to do right by her family, no matter what. Margaret's routine has always included solving one emergency after another with quick decision.
So when her eldest son Beau's lover washers up on the beachfront in front of their house, she does the only thing an unflinchingly devoted mother could: she hides the body to protect her son. Now unexpectedly, in the aftermath of this desperate act, emerges Alek Spera, who knows about the death and the secret life of her son. But what begins as a riveting cat-and-mouse game soon turns into a haunting love story with self-sacrifice at its center.
For as Margaret attempts to dodge blackmail, the law and even the questions of her family, she herself becomes exposed.